英文:
GStreamer: how to read mp4 frame by frame and extract capture (camera) time? Need to find closest to given ts frame
问题
给定一些时间戳（可能是秒或毫秒精度），我需要从 mp4 文件中提取与假定的摄像头时间戳（捕获时间，而不是 pts 或 dts）最接近的帧，那么更合适的流程是什么，以提取每个帧在其捕获时间戳内（类似于使用缓冲区中的 GetReferenceTimestampMeta）？考虑到我使用 gstreamer-sharp，我希望使用 appsink 事件，类似于：
private static void AppSink_NewSample(object o, NewSampleArgs args)
{
if (o is AppSink aps)
{
var sample = aps.PullSample();
var buf = sample.Buffer;
buf.Map(out var info, MapFlags.Read);
//application/x-rtp
var tsMeta = buf.GetReferenceTimestampMeta();
//NOTE tsMeta 不应为 null...
//TODO 一些时间戳比较逻辑
buf.Unmap(info);
}
Counter++;
}
简而言之，我需要遍历帧并基于某些条件（实际上是最接近给定时间戳的条件）选择其中之一。
提前感谢。
英文:
Given some timestamp (probably second or ms precision), I need to exctract closest frame
in mp4 file with assumed camera timestamp(captured time, not pts or dts) for each frame, what is a more appropriate pipeline to exctract each frame within it's captured timestamp (smth like to use GetReferenceTimestampMeta from buffer)? Given that I work via gstreamer-sharp I expect to use appsink events, smth like:
private static void AppSink_NewSample(object o, NewSampleArgs args)
{
if (o is AppSink aps)
{
var sample = aps.PullSample();
var buf = sample.Buffer;
buf.Map(out var info, MapFlags.Read);
//application/x-rtp
var tsMeta = buf.GetReferenceTimestampMeta();
//NOTE tsMeta shouldn't be null there...
//TODO some timestamps compare logic
buf.Unmap(info);
}
Counter++;
}
Put it simple -- I need to iterate over frames and select one based on some condition (actually, closest to given timestamp).
Thanks in advance.
答案1
得分: 0
我找到了方法，它类似于：
var appSink = (AppSink)readerPipe.GetByName("my_appsink");
readerPipe.SetName("frame_stepper");
var q = readerPipe.SetState(State.Playing);
var step = 1;
while (step < frameNumber)
{
appSink.PullSample();
step++;
}
英文:
I found the way, it is smth like:
var appSink = (AppSink) readerPipe.GetByName("my_appsink");
readerPipe.SetName($"frame_stepper");
var q = readerPipe.SetState(State.Playing);
var step = 1;
while (step < frameNumber)
{
appSink.PullSample();
step++;
}
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